any visible deviation of character in a well-established breed
is rejected as a blemish; but it by no means follows that at an early
period, before well-marked breeds had been formed, such deviations would
have been rejected; on the contrary, they would have been eagerly preserved
as presenting a novelty, and would then have been slowly augmented, as we
shall hereafter more clearly see, by the process of unconscious selection.

I have made numerous measurements of the various parts of the body in
the several breeds, and have hardly ever found them quite the same in
birds of the same breed,--the differences being greater than we
commonly meet with in wild species. To begin with the primary feathers
of the wing and tail; but I may first mention, as some readers may not
be aware of the fact, that the number of the primary wing and tail
feathers in wild birds is generally constant, and characterises, not
only whole genera, but even whole families. When the tail-feathers are
unusually numerous, as for instance in the swan, they are apt to be
variable in number; but this does not apply to the several species and
genera of the Columbidae, which never (as far as I can hear) have less
than twelve or more than sixteen tail-feathers; and these numbers
characterise, with rare exception, whole sub-families.[301] The wild
rock-pigeon has twelve tail-feathers. With {159} Fantails, as we have
seen, the number varies from fourteen to forty-two. In two young birds
in the same nest I counted twenty-two and twenty-seven feathers.
Pouters are very liable to have additional tail-feathers, and I have
seen on several occasions fourteen or fifteen in my own birds, Mr. Bult
had a specimen, examined by Mr. Yarrell, with seventeen tail-feathers.
I had a Nun with thirteen, and another with fourteen tail-feathers; and
in a Helmet, a breed barely distinguishable from the Nun, I have
counted fifteen, and have heard of other such instances. On the other
hand, Mr. Brent possessed a Dragon, which during its whole life never
had more than ten tail-feathers; and one of my Dragons, descended from
Mr. Brent's, had only eleven. I have seen a Baldhead-Tumbler with only
ten; and Mr. Brent had an Air-Tumbler with the same number, but another
with fourteen tail-feathers. Two of these latter Tumblers, bred by Mr.
Brent, were remarkable,--one from having the